Flame-retardant textiles by reaction of cellulose with the adduct of phosphorus trichloride and N,N-dimethylformamide

ABSTRACT

The preparation in textile form of a cellulose N,Ndimethylorthoformamoylphosphorochloridite ester possessing flame and wrinkle resistance is described. The preparation is accomplished by preswelling the cellulose for 1 to 60 minutes in N,N-dimethylformamide, followed by reaction of the cellulose with 1-30% concentrations of phosphorus trichloride-N,Ndimethylformamide adduct in excess N,N-dimethylformamide as solvent, with or without an inert diluent, at 20-60* C for 1 to 180 minutes. After the reaction has been carried out to the desired extent of completion the modified cellulose is washed with an inert solvent. The modified cellulose contains nitrogen, phosphorus, and chlorine in a ratio of 1:1:1. If desired, the product can be freed of chlorine by subsequent washing in ice water, or may be used directly as an intermediate for further modification.

v United States Patent [191 Vigo et a1.

[4 1 Nov. 18,1975

[75] Inventors: Tyrone L. Vigo, Kenner; Clark M.

Welch, Metairie, both of La.; Anna M. Collins, College Park, Ga.

[73] Assignee: The United States of America as represented by theSecretary of Agriculture, Washington, DC.

[22] Filed: Jan. 28, 1974 [21] Appl. No.: 437,096

[52] US. Cl. 8/188; 8/116 P; 260/219 [51] Int. Cl. D06M 13/46 [58] Fieldof Search 8/116 P, 188

Vigo et a1., -Reaction of Cellulose with PCL DMF Adduct, Journal ofApplied Polymer Science, Vol. 17, No. 2, pp. 571-584 (1973), registeredpublication date of Mar. 13, 1973.

Primary Examiner-Murray Tillman Assistant Examiner-Arthur H. KoeckertAttorney, Agent, or FirmM. Howard Silverstein; Max D. Hensley ABSIRACTThe preparation in textile form of a cellulose N,N-dimethylorthoformamoylphosphorochloridite ester possessing flame andwrinkle resistance is described. The preparation is accomplished bypreswelling the cellulose for 1 to 60 minutes in N,N-dimethylformamide,followed by reaction of the cellulose with l-30% concentrations ofphosphorus trichloride-N,N-dimethylformamide adduct in excessN,N-dimethylformamide as solvent, with or without an inert diluent, at20-60C for 1 to 180 minutes. After the reaction has been carried out tothe desired extent of completion the modified cellulose is washed withan inert solvent. The modified cellulose contains nitrogen, phosphorus,and chlorine in a ratio of 11111. If desired, the product can be freedof chlorine by subsequent washing in ice water, or may be used directlyas an intermediate for further modification.

8 Claims, No Drawings FLAME-RETARDANT TEXTILES BY REACTION OF CELLULOSEWITH THE ADDUCT F PHOSPI-IORUS TRICI-ILORIDE AND N,N-DlMETI-IYLFORMAMIDEThis invention relates to a method of imparting flame and wrinkleresistance to cellulosic textile materials by reaction of the cellulosewith anadduct which phosphorus trichloride forms withN,N-dimethylformamide.

More specifically, the present inventionrelates to the conversion offibrous cellulose in the form of yarn or.

fabric into phosphorus-, nitrogen-, and halogen-containing cellulosictextiles having flame resistance and improved wrinkle recovery, byreaction of the cellulose with phosphorustrichloride-N,N-dimethylformamide adduct in aprotic solvents.

The main object of the present invention is to impart flame resistanceto cellulosic textiles by chemical modification of the cellulose bymeans of a phosphorus trichloride adduct with N,N-dimethylformamide.

A second object of the present invention is to provide a means ofintroducing a limited degree of cellulose crosslinking in cellulosicfabrics, so as to impart increased wrinkle resistance in the wet and drystates.

A third object of the present invention is to :provide ameans ofintroducing phosphorus,- and nitrogen-containing substituents, as wellas chlorine, into fibrous.

of the original un-- of the prior processes depend for theireffectiveness on:

bringing the cellulose derivative into solution so as to facilitatereaction with phosphorus trichloride. For example, in U.S. Pat. No.2,489,225 (Nov. 22,

1949), phosphorus trichloride is reaotedwith soluble cellulose etherorester derivatives: The degree of;'sub-- stitution of the modifiedcellulose ether or ester isthat I necessary to render the cellulosicmaterial. soluble in organic solvents or in phosphorus trichloride. Sucha.

process is not suitable for treatment of native cellulose when it is.desired to retain the fiber, yarn of fabric structure which thecellulose originally possesses. Likewise, recent work by Dimitrov, etal. (Cellulose Chem.

Technol, 1968, 2(4), 375-389) describes the reaction of phosphorustrichloride with a cellulosic derivative (5,6-celluloseen) in which'anolefinic group must be present in order for the cellulose to react withthe phosphorus trichloride. The phosphorus halide adds across theolefinic double bond in this instance.

The present invention makes it possible for the first time to reactphosphorus trichloride with unsubstituted permits retention of theoriginal fiber, yarn and fabric structure by the cellulosic textile.

Another major advantage ofthe present process over prior art is that itsimultaneously introduces, in a onestep process, nitrogen as well asphosphorus into the cellulose, and in doing so, produces a producthaving high flame resistance as well as improved wrinkle recovery It iswell known that nitrogen and phosphorus have a synergistic effect inimparting flame retardancy to cellulose.

A further advantage of the present process is that pretreatment of thecellulose with 'N,Ndimethylformamide activates the cellulose, andgreatly increases its rate' of reaction towards the phosphorustrichloride- N;N-dimethylformamide adduct. Such an increase is essentialto obtain the high phosphorus and nitrogen contents necessary in thecellulosic product for adequate flame and. wrinkle resistance. Otheradvantages will becomeapparent inthe description that follows.

The processes of this invention are applicable to cellulosederived fromcotton or wood pulp, whieh cellulose may benative, mercerized, orregenerated, and which may be in the form of loose fibers, silver. yarnor fabric.

The above advantages of the present invention are unexpectedly obtainedby .using a phosphorus trichloride adduct with.N,N-dirnethylformamide inthe treatment of cellulose.

The phosphorus-trichloride adduct with'N,N-dimethylformamide is formedby reaction of phosphorus trichloride with -N,N-dimethylformamide atO30C in the absence of air and moisture. The reaction is nearlyinstantaneous, andzmay becarried out using excess 1N,N-dimethylformamide as both'reactant and solvent,

or may beJcarried outas described in the literature IT. D. Smith, J.Chem.'.Soc.,'841 (1966)] using an inert diluent such as carbontetrachloride. The mole ratio of phosphorus trichloride toN,N-dimethylformamide in the adduct is known to be 1:2. The structure ofthe adduct has previously been established by Smith as Cl-F'.[.OClrl=lI(Cl'l 2C1.

lncarrying out the processes of the present inven tion, the l:2 adductof phosphorus trichloride with dimethylformamide does not need to beisolated or purified, but can be used directly as formed in solution inexcess dimethylformamide, with or without other diluents present. Thepresence of excess dimethylformamide minimizes cellulose degradation andtendering during reaction of the adduct with the cellulose, and istherefore preferred. The reaction between cellulose and the adduct isthought to proceedas follows:

-continued C1 C1 O-Cell where Cell-OH is a portion ofa molecular chainof celdrying, prior to immersion in the N,N-dimethylforma lulose and Ris a methyl group. The product, herein remide. ferred to as a celluloseN,N-dimethylorthoformamoyl- Removal of excess N,N-dimethylformamide orother phosphorochloriditc ester, is found to contain phostertiary amidesin step (b) above, may be accomplished phorus, nitrogen, and chlorine inan atomic ratio of by ordinary mechanical methods of wringing, such as111:]. Subsequent treatment with water produces the passing the fabricthrough squeeze rolls, centrifugation, following reactions: draining, orby pressing the cellulose against a filter.

The relative proportions of nitrogen and chlorine lost The reaction ofthe cellulosic textile with the adduct depends on the relative extent towhich these hydroof phosphorus trichloride and N,N-dimethylformamidelytic reactions are carried to completion. Formation of 25 as specifiedin step (0) above, in preferably carried out a labile formate derivativeduring hydrolysis is indiin N,N-dimethylformamide as the reactionsolvent, cated by increased infrared absorption at 5.75-5.85 since thissolvent maintains the cellulose in a swollen mp characteristic of thecarbonyl group in formates. state; and since the above adduct hasconsiderably sol- The treatment of cellulose by the processes of theubility in this medium. At concentrations above by present inventioncomprises the following steps: 30 weight ofN,N-dimethylformamide-phosphorus trichloa. immersion ofair-equilibrated, fibrous cellulose in ride adduct, it is necessary touse an inert diluent such textile form in N,N-dimethylformamide at atemperaas chloroform, methylene chloride, carbon tetrachloture of aboutfrom C to C for a period of from I ride, or perchloroethylene, as partof the solvent system minute to 60 minutes to swell the fibers, toinsure solubility of the adduct before it is reacted b. removal ofexcess N,N-dimethylformamide from with the cellulose. the swollencellulose. The weight ratio of the phosphorus trichloride-amide c.immersion of the cellulosic textile in a solution adduct to cellulosewhich may be used can be varied containing about from 1% to 30% byweight of the 1:2 over a wide range. The most practical ratio to usedeadduct of phosphorus trichloride with N,N-dimethylpends to some extenton whether the cellulose is in the formamide together with an inertaprotic diluent seform of loose fibers, silver, yarn or fabric, sincethe relected from the class consisting of chloroform, carbon activity ofthe cellulose varies with the form of cellulose tetrachloride, methylenechloride and perchloroethylbeing treated. The preferred ratio alsovaries with the ene at a temperature of from 20C to 60C for about degreeof flame resistance and improvement in wrinkle from 1 minute to 180minutes, in order to obtain reacrecovery desired in the cellulose, butusually is in extion of the cellulose with the adduct, ce ss of 1 partby weight of the adduct to 5 parts by d. washing the cellulosic textilewith N,N-dimethylweight of the cellulose. The concentration of thephosformamide to remove unreacted adduct, phorus trichloride-amideadduct may be varied conside. washing the cellulosic textile with an'inert solvent erably, but above a concentration of 30% by weight,selected from the group consisting of benzene and the reactions withcellulose slows down considerably, chloroform, to removeN,N-dimethylformamide, and little practical benefit results from the useof higher f. washing the cellulosic textile with ice water. and ratios.then washing at room temperature with water contain- By adjusting thephosphorus trichloride-amide ading 0-10% acetic acid, to remove tracesof combined duct concentration and the reaction time, the extent ofchlorine and reagent and solvents, and reaction of the adduct with thecellulose can be varied g. drying the textile. considerably, so that thephosphorus contentobtained The immersion of the cellulose inN,N-dimethylforin the modified cellulose is in the range of 0.6% to 6%,mamide, as specified in step (a) above, is critical to the the nitrogencontent is in the range of 0.1% to 2.5%, process, in that this stepswells the cellulose fibers and and the chlorine content is in the rangeof 0.1% to 6%. greatly increases the rate of subsequent reaction of theStep (d) removes the unreacted phosphorus tricellulose with the adductof phosphorus trichloride and chlorideamide adduct. Step (e) removesN,N-dimethyl- N,N-dimethylformamide. The cellulose to be used informamide. Step (e) can be omitted when the modified this process shouldbe at equilibrium with the atmocellulose is to be water-washed as instep (j). Washing sphere at ordinary humidity so that the moistureconstep (j) is omitted when it is desired to maintain the tent causesthe fibers to be much more accessible to PCl bond in the modifiedcellulose for further reacswelling by N,Ndimethylformarnide and tosubsequent tion with other substrates. The cellulose N,N-dimereactionwith the adduct of phosphorus trichloride andthylorthoformamoylphosphorochloridite ester ob- N,N-dimethylformamide.The cellulose should not be tained can be reacted with active hydrogencompounds subjected to any deswelling treatment such as ovensuch asamines, alcohols, and mercaptans to yield other derivatives of cellulosein textile forma During the wash with ice water, partial hydrolysisoccurs as already indicated in the above equations, and most of thecombined chlorine in the product is removed. A portion of the combinednitrogen in the product is also lost in this washing step. The wash withice water is preferably followed by a wash with l aqueous acetic acidwhen the adduct concentration used in treating the cellulose is 10% orless. The acetic acid decreases the binding of metal ions present in thewash water by the substituted cellulose, and thus renders the flameretardancy more durableto washing.

1n the examples that follow, fabric breaking strength (strip method) wasdetermined by the procedure of ASTM-Dl682-64, using a Scott tester.Wrinkle recovery was determined by the Monsanto method (ASTM D-l295-67).Flame resistance was measured by the standard vertical flame testdescribed in US. Federal Supply Service, Textile Test Methods,.F'ederalTest Method Std. No. 191, Method 5903.1, and by the match or clock testdescribed by Reeves, et al. [Text. Res. J. 23, 527-532 (1953)].Durability to laundering of the treated fabrics was determined byrepeated washing and drying in an agitator-type washer and a tumbledryer under normal conditions for cotton (10 minutes hot water wash, 30minutes high temperature drying) using a commercial phosphate detergent.All parts and percentages are by weight. The phosphorustrichloride-amide adduct concentrations specified are based on the 1:2adduct of phosphorus trichloride with the amide, and in the cases whereN,N-dimethylformamide is the amide used, the adduct concentrationspecified is 2.07 times the percentage by weight of phosphorustrichloride added in making up the treating solution. The cotton clothused for fabric treatments was desized, scoured, and bleached sateenweighing 8 oz. per sq. yd. N,N-dimethylformamide is hereafterabbreviated DMF.

EXAMPLE 1 Reaction of Cotton Fabric with Phosphorus Trichloride-DMFAdduct in DMF at Low Adduct Concentrations Desized, scoured, andbleached 8 oz./yd. cotton sateen fabric was immersed in excessN,N-dimethylformamide (DMF) for 30 minutes at 25C, put throughlaboratory wringers to remove excess DMF, and then reacted for minutesat 25C with 5% phosphorus trichloride-DMF adduct in DMF in a stopperedflask with agitation, utilizing 40 grams of solution per gram of cotton.This solution was prepared by adding 2.4 parts of phosphorus trichlorideto 97.6 parts by weight of DMF. The fabric was subsequently washed threetimes with excess DMF, then with ice water, immersed in 5% aqueousacetic acid for 10 minutes, washed with tap water for 1 minute, andallowed to air-dry to constant weight. The resultant fabric had anadd-on of 9.8%, and the following elemental composition: %P, 1.8; %N,0.6; %Cl, 0.02; %Ca, 0.02. The fabric had a char length of 3.75 inchesas measured by the standard vertical flame test and possessed noafterglow; untreated sateen fabric had extensive afterglow, very littlechar, and burned the entire fabric length (10 inches) under comparabletest conditions. The breaking strength of the treated fabric was 90 lbs.while that of the untreated fabric was 137 lbs. The conditioned and wetwrinkle recoveries (warp fill) of the treated fabric were respectively215 and 222, while those of the untreated fabric were respectively 183and 168. Fibers of the treated fabric were insoluble in 0.5 M aqueouscupriethylenediamine solution, even after 10 minutes standing, whereasfibers of untreated fabric dissolved within 15-30 seconds. This showsthat the treated cotton cellulose was highly crosslinked. The cellulosecrosslinking imparted by the process of this invention was responsiblefor the wrinkle resistance imparted.

EXAMPLE 2 Reaction of Cotton Fabric with Phosphorus Trichloride-DMF inDMF at Intermediate Adduct Concentrations Cotton sateen fabric wasimmersed in excess DMF for 30 minutes at 25C, put through laboratorywringers to remove excess DMF, then reacted for 15 minutes at 25C with15% phosphorus trichloride-DMF adduct in DMF in a stoppered flask withagitation, utilizing 40 grams of solution per'gram of cotton. Thissolution was prepared by adding 7.2 parts of phosphorus trichloride to92.8 parts of DMF. The fabric was then washed three times with excessDMF, once with chloroform, and allowed to air-dry to constant weight.The resultant fabric had an add-on of 19.0%, a match test angle of 180,and the following elemental composition: %P, 2.8; %N, 1.1; Cl, 25; Ca,0.01, and was suitable for further reaction utilizing the reactive PCllinkage. The atomic ratio of phosphorus, nitrogen, and chlorine in thisproduct was 1.3: 1.1:1.0, or approximately 111:].

EXAMPLE 3 Reaction of Cotton Fabric with Phosphorus Trichloride-DMF inDMFCHCI at High Adduct Concentrations Cotton sateen fabric was immersedin excess DMF for 30 minutes at 25C, put through laboratory wringers toremove excess 'DMF, then reacted for 1 hour at 25C with 25% phosphorustrichloride-DMF adduct- 59% DMF-16% chloroform in a stoppered flask withagitation, utilizing. 40 grams of solution per gram of cotton. Thissolution was prepared by adding 12.1 parts of phosphorus trichloride to87.9 parts of a 3.7:] mixture by weight of DMF and chloroform. Thefabric was then washed with excess DMF, ice water, and tap water inexcess for 30 minutes, and allowed to air-dry overnight. The resultantfabric possessed 3.9% P, 0.6% N, 0.3% Ca, and 0.4% Cl, and had a charlength of 2.5 inches. Fibers of the treated fabrics were insoluble in0.5 M cupriethylenediamine solution indicating the cellulose was highlycrosslinked. After 20 standard home launderings (wash and tumble drycycles) using a commercial phosphate detergent in the wash cycle, thefabric possessed 5.2% P, 0.3% N, 1.2% Ca, and 0.8% Cl, and still passedthe standard vertical flame test with a char length of 3.5 inches.

EXAMPLE 4 Reaction of Cotton Fabric with Phosphorus Trichloride-DMFAdduct in DMF with Omission of Preswelling Step.

Cotton sateen fabric was immersed in 5% phosphorus trichloride-DMF inDMF for 15 minutes at 25C with agitation, utilizing 40 grams of solutionper gram of cotton. This solution was prepared by adding 2.4 parts ofphosphorus trichloride to 97.6 parts of DMF. The fabric was then washedwith DMF, ice water, aqueous acetic acid for minutes, tap water for 1minute, and allowed to air-dry. The resultant fabric had a weight gainof only 0.7%. and only 0.1% P, 0.05% N, with trace amounts of chlorineand calcium. Although the fabric possessed no afterglow, it had a 0angle by the match test, and was therefore unsuitable for testing by thestandard vertical flame test method. The results show that it isnecessary to preswell the cellulose in DMF to obtain a useful degree ofreaction by the processes of the present invention.

EXAMPLE 5 Reaction of Cotton Fabric with the Phosphorus TrichlorideAdduct ofN,N-dimethylacetamide in DMF Cotton sateen fabric was immersedfor 30 minutes in excess DMF, then put through wringers to remove excessDMF, then reacted with agitation in a stoppered flask containing 5%phosphorus trichloride-N,N-dimethylacetamide adduct dissolved in DMF,there being 40 grams of solution per gram of cotton. This reaction wasrun at C for 1 hr. The solution was prepared by adding 2.2 parts ofphosphorus trichloride to 2.8 parts of N.N-dimethylacetamide withcooling to maintain a temperature not exceeding 50C. The resultingsolution was dissolved in 95 parts of DMF. The resultant fabric waswashed with DMF, ice water, tap water for minutes, and allowed toair-dry. The fabric, although having no afterglow when ignited, had amatch test angle of 0, and was therefore not acceptable for furtherflammability testing. Elemental analysis of the fabric gave thefollowing results: P--0.1, %N-0.15, Cl0.03, Ca-0.l3. Conducting thereaction using N,N-dimethylacetamide as the preswelling agent, anddissolving the adduct in N,N-dimethylacetamide gave comparable results.This example proves that N,N- dimethylacetamide cannot be used in placeof DMF in the processes of the present invention.

EXAMPLE 6 Reaction of Cotton Fabric with PhosphorusTrichloride-N-Methylpyrrolidone Adduct in DMF Cotton sateen fabric wasimmersed for 30 minutes in excess DMF. and was then put through wringersto remove excess DMF. The fabric was immersed with agitation in astoppered flask containing 5.9%- phosphorustrichloride-N-methylpyrrolidone adduct dissolved in DMF, there beinggrams of solution per gram of cotton. The reaction was run at 25C for 1hr. The solution was prepared by adding 3.5 parts N-methylpyrrolidone to2.4 parts of phosphorus trichloride with cooling, and later adding 94.1parts of DMF. The resultant fabric was washed as in Example 1, andpossessed only 0.1% phosphorus, and trace amounts of nitrogen, chlorine,and calcium. It had a match test angle of 0 and was thereforeunacceptable for use as a flame-retardant fabric. Repeating the reactionusing N-methylpyrrolidone in the preswelling step as' well as in thereaction gave comparable results. This example shows that N-methylpyrrolidone cannot be used in place of DMF in the processes of thepresent invention.

EXAMPLE 7 Reaction of Cotton Fabric with PhosphorusTribromide-N,N-Dimethylformamide Adduct in DMF Cotton sateen fabric wasimmersed for 30 minutes in excess DMF, then put through wringers toremove excess DMF, and reacted with agitation in a stoppered flaskcontaining 5% phosphorus tribromide-N,N-dimethylformamide adductdissolved in DMF utilizing 40 grams of solution per gram of cotton. Thissolution was prepared by adding 3.2 parts of phosphorus tribromide to96.8 parts of DMF. The reaction was run for 1 hr. at 25C. The resultantfabric was washed as in Example 1, and possessed 0.5% P, 0.2% N, 0.1%Br, and trace amounts of calcium. lt had a match test angle of 45, andtherefore possessed some flame resistance, but not enough to be ofpractical benefit. The results show that phosphorus tribromide cannot besubstituted for phosphorus trichloride in the processes of ourinvention.

EXAMPLE 8 Reaction of Cotton Yarn with PhosphorusTrichloride-N,N-Dimethylformamide Adduct in DMF Kiered 12/3 cotton yarnwas immersed for 30 minutes in excess DMF, then centrifuged to removeexcess DMF, and reacted with agitation in a stoppered flask containing15% phosphorus trichloride-N.N-dimethylformamide adduct in DMF utilizing40 grams of solution per gram of cotton. The reaction was run at 25C for1 hr. This solution was prepared by adding 7.2'parts of phosphorustrichloride to 92.8 parts of DMF. The resultant yarn was washed as inExample 2, and possessed 3.9% P, 0.2% N, and 0.5% Cl. It had a matchtest angle of quite acceptable for a flame resistant cotton textile.

We claim:

1. A process for preparing a fibrous crosslinked N,N-dimethylorthoformamoylphosphorochloridite ester of cellulose in textileform, which ester is characterized by its containing nitrogen,phosphorus, and chlorine in a 1:1:1 atomic ratio, said processcomprising:

a. immersion of a fibrous cellulose textile in N,N-

dimethylformamide at a temperature of about from 20C to 30C for a periodof from 1 minute to 60 minutes to swell the fibers,

b. removal of excess N,N-dimethylformamide from the swollen cellulose,

c. immersion of the cellulosic textile in a solution containing aboutfrom 1% to 30% by weight of the 1:2 adduct of phosphorus trichloridewith N,N- dimethylformamide, in a solvent containing 50%l00%N,N-dimethylformamide together with an inert aprotic diluent selectedfrom the class consisting of chloroform, methylene chloride, carbontetrachloride and perchloroethylene, at a temperature of from 20C to 60Cfor about from 1 minute to minutes, in order to obtain reaction of thecellulose with the aforesaid adduct,

d. washing the cellulosic textile with N,N-dimethylformamide to removeunreacted adduct,

e. washing the cellulosic textile with a solvent selected from the groupconsisting of benzene and chloroform, to remove the N,N-dimethylformamide, and

f. drying the textile.

2. The process of claim 1 wherein the textile is in the form of a yarn.

3. The process of claim 1 wherein the textile is in the form of afabric.

4. As a textile material, the fibrous crosslinked N,N-dimethylorthoformamoylphosphorochloridite ester of cellulose produced bythe process of claim 1.

5. A process for preparing a fibrous, crosslinked, partially hydrolyzedN,N-dimethylorthoformamoylphosphite ester of cellulose in textile form,which ester is characterized by its nitrogen and phosphorus content, theabsence of combined chlorine, and by its flame resistance and wrinkleresistance, said process comprising:

a. immersion of a fibrous cellulose textile in N,N-

dimethylformamide at a temperature of about from 20C to 30C for a periodof from 1 minute to 60 minutes to swell the fibers,

b. removal of excess N,N-dimethylformamide from the swollen cellulose,

c. immersion of the cellulosic textile in a solution containing aboutfrom 1% to 30% by weight of the 1:2 adduct of phosphorus trichloridewith N,N- dimethylformamide, in a solvent containing 50%lN,N-dimethylformamidetogether with an inert aprotic diluent selectedfrom the class consisting of chloroform, methylene chloride, carbontetrachloride, and perchloroethylene, at a tempe rature of from 20C to60C for about from 1 minute to minutes, in order to obtain reaction ofthe cellulose with the aforesaid adduct,

d. washing the cellulosic textile with N,N-dimethylformamide to removeunreacted adduct.

e. washing the cellulosic textile with ice water and then washing atroom temperature with water containing 040% acetic acid, to removetraces of reagents and solvents and combined chlorine, and

f. drying the textile.

6. The process of claim 5 wherein the textile is in the form of a yarn.

7. The process of claim 5 wherein the textile is in the form of afabric.

8. As a textile material, the fibrous crosslinked partially hydrolyzedN,N-dimethylorthoformamoylphosphite ester of cellulose produced by theprocess of

1. A PROCESS FOR PREPARING A FIBROUS CROSSLINKEDN,N-DIMETHYLORTHOFORMAMOYLPHOSPHOROCHLORIDITE ESTER OF CELLULOSE INTEXTILE FORM, WHICH ESTER IS CHARACTERIZED BY ITS CONTAINING NITROGEN,PHOSPHORUS, AND CHLORINE IN A 1:1:1 ATOMIC RATIO, SAID PROCESSCOMPRISING: A. IMMERSION OF FIBROUS CELLULOSE TEXTTILE INN,N-DIMETHYLFORMAMIDE AT A TEMPERATURE OF ABOUT FROM 20*C TO 30*C FOR APERIOD OF FROM 1 MINUTE TO 60 MINUTES TI SWELL THE FIBERS, B. REMOVAL OFEXCESS N,N-DIMETHYLFORMAMIDE FROM THE SWOLLEN CELLULOSE, C. IMMERSION OFTHE CELLULOSIC TEXTILE IN A SOLUTION CONTAINING ABOUT FROM 1% TO 30% BYWEIGHT OF THE 1:2 ADDUCT OF PHOSPHORUS TRICHLORIDE WITHN,N-DIMETHYLFORMAMIDE, IN A SOLVENT CONTAINING 50%-100%N,N-DIMETHYLFORMAMIDE TOGETHER WITH AN INERT APROTIC DILUENT SELECTEDFROM THE CLASS CONSISTING OF CHLOROFORM, METHYLENE CHLORIDE, CARBONTETRACHLORIDE AND PERCHLOROETHYLENE, AT A TEMPERATURE OF FROM 20*C TO60*C FOR ABOUT FROM 1 MINUTE TO 180 MINUTES, IN ORDER TO OBTAIN REACTIONOF THE CELLULOSE WITH THE AFORESAID ADDUCT, D. WASHING THE CELLULOSICTEXTILE WITH N,N-DIMETHYLFORMAMIDE TO REMOVE UNREACTED ADDUCT, E.WASHING THE CELLULOSIC TEXTILE WITH A SOLVENT SELECTED FROM THE GROUPCONSISTING OF BENZENE AND CHLOROFORM, TO REMOVE THEN,N-DIMETHYLFORMAMIDE, AND F. DRYING THE TEXTILE.
 2. The process ofclaim 1 wherein the textile is in the form of a yarn.
 3. The process ofclaim 1 wherein the textile is in the form of a fabric.
 4. As a textilematerial, the fibrous crosslinkedN,N-dimethylorthoformamoylphosphorochloridite ester of celluloseproduced by the process of claim
 1. 5. A process for preparing afibrous, crosslinked, partially hydrolyzedN,N-dimethylorthoformamoylphosphite ester of cellulose in textile form,which ester is characterized by its nitrogen and phosphorus content, theabsence of combined chlorine, and by its flame resistance and wrinkleresistance, said process comprising: a. immersion of a fibrous cellulosetextile in N,N-dimethylformamide at a temperature of about from 20*C to30*C for a period of from 1 minute to 60 minutes to swell the fibers, b.removal of excess N,N-dimethylformamide from the swollen cellulose, c.immersion of the cellulosic textile in a solution containing about from1% to 30% by weight of the 1:2 adduct of phosphorus trichloride withN,N-dimethylformamide, in a solvent containing 50%-100%,N,N-dimethylformamide together with an inert aprotic diluent selectedfrom the class consisting of chloroform, methylene chloride, carbontetrachloride, and perchloroethylene, at a temperature of from 20*C to60*C for about from 1 minute to 180 minutes, in order to obtain reactionof the cellulose with the aforesaid adduct, d. washing the cellulosictextile with N,N-dimethylformamide to remove unreacted adduct, e.washing the cellulosic textile with ice water and then washing at roomtemperature with water containing 0-10% acetic acid, to remove traces ofreagents and solvents and combined chlorine, and f. drying the textile.6. The process of claim 5 wherein the textile is in the form of a yarn.7. The process of claim 5 wherein the textile is in the form of afabric.
 8. As a textile material, the fibrous crosslinked partiallyhydrolyzed N,N-dimethylorthoformamoylphosphite ester of celluloseproduced by the process of claim 5.